88 MEMOmS OF THE NATIONAL ACADEMY OF SCIENCES. 



is about lialf as long as the teriuiual joiut. The hind legs are somewhat stouter and the middle 

 pair a little shorter than the others; but otherwise they closely resemble each other. 



The dilterent segments of the thorax, as stated, are protected above by the development of 

 distinct chitinous plates, the lower edges of which are clearly marked, and extend downward to 

 the concealment, on a si(ie view, of the lower part of the body. The abdomen, however, seems to 

 have no such specialization of the integument of the upper surtace. It is stout, apparently well 

 rounded transversely, and tapers to a i.roduced but blunt tip, which is armed with a pair of 

 slightly recurved stout claws, two or three times longer than the leg-claws, arranged as if to drag 

 the body backward. The abdomen is faintly divided into four segments, often entirely obscured. 

 Of these the terminal usually appears shorter than the others, which are subequal. 



These divisions of the body are all that appear to have belonged to the animal; and it is the 

 most remarkable fact in its organization that it certainly had no distinct chitinous head. This is 

 the more surprising from the clearness with which the thoracic segments are marked. All that 

 one can lind preserved is what appears to be a ring of buccal plates terminating anteriorly the 

 alimentary canal, and which was evidently capable of being thrust forward a long distance beyond 

 the body. If it were not for the unusual preservation of the alimentary canal we should be forced 

 to consider the head as lost from all the specimens, notwithstanding the nearly perfect preserva- 

 tion of the other parts; but in several specimens the alimentary tube can be traced with ease half 

 throvh the body, terminating in front in these more or less clearly preserved chitinous plates, 

 arranged to form a circle a little smaller than the coxal cavities. What is most remarkable is the 

 extension of this alimentary tube and accompanying buccal plates like a ])roboscis far beyond the 

 limits of the body; sometimes forward (apiiarently through the anterior notch) to a distance in 

 front of the first segment equal to half the length of the latter; more often directed downward as 

 well as outward, perhaps between the front legs, ami occasionally extending beyond the body to 

 nearly or (pnte th' mfin- Inuith of the same. It seems to leave its direct course within the body 

 at about the middle of the'tirst thoracic segment, directly in front of which position the buccal 

 plates appear in one or two specimens, apparently in the position ot repose. The various i)Ositions 

 in which these buccal plates are found outside the body, both when their connection with the tube 

 is traceable and when it is obscure or fails, shows how perfectly movable a proboscis the creature 

 possessed. The external parts of the head, then, may be said to have probably been composed 

 entirely of a flexible, extensible membrane capable of protrusion as a fleshy i)roboscis, separated 

 by no line of demarkation from the first thoracic segment, and bearing as appendages only a series 

 of buccal plates for mouth-parts, and beyond this nothing— neither cranium, eyes, antenuie,nor palpi. 

 In the absence of eyes, one would naturally look for the development of tactile organs ot some sort; 

 but nothing of the kind is discoverable on the most careful special search, unless such an office 

 may be performed by long delicate hairs which seem, in some few instances, to be scattered dis- 

 tantly over the projected mouth-tube. 



A special study of the buccal plates in the twenty-four or twenty-five specimens which best 

 show them gives no very satisfactory explanation of their form and relations. They have been said 

 to form a ring, because in a considerable number they are so arranged; but it may be doubted 

 whether this appearance is not due to the flaking of the chitinous parts. Like the lips of the 

 notches of the thoracic segments, the buccal apparatus was evidently more dense and thicker than 

 other te-umeutary parts, for these are darker colored than the other parts and often carbonaceous 

 in this condition the central portions seem liable to flake away and leave the thinner edges with 

 ragged fragments of the carbonaceous inner portions attached, thus frequently lormmg a sort ot 

 irregular ring of dark chitiue. On the other hand, it is just as common for fragments to become 

 chipped out from the edges, or for rounded bits to fall out here and there, producing thereby an 

 almost endless varietv of present appearances. Among these it is difficult to trace tlie clew to the 

 original arrangement and form of the plates. One might anticipate that these would have occurred 

 around the central orifice of a proboscis; and if anything of this sort was present it would appear 

 the most probable (though extremely doubtful) that there were four subtriangular plates ol pretty 

 large size, the lateral the larger, nearly meeting by their tips at the center. From specimens, 

 however, which are least broken, it would seem quite as probable that the api)aratus consisted of 

 two attiiigeiit or overlapping circular plates, placed transversely, densest centrally, wliich by tlieir 



